I'm not sure why conservatives keep bringing up the "but this woulda been a senior moment for McCain!" specter when it comes to what they perceive are Barack Obama gaffes (and what actually appear to be some guy behind him continually talking through his speech). The most famous version of the media harping on "senior moments" is Fox News' 64-year-old Brit Hume attempting to excuse a McCain flub, which would seem to sort of counteract the idea of McCain's base going after him.
I remember when Marc Ambinder did this a couple of months back, too. It's one thing to declare that something McCain did shouldn't be declared a senior moment (I'm of the full belief that he has the ability to fuck up just as well as a man half his age), but the idea that you can simply create a press corps ravenously scouring for any hint of McCain's age peeking through and triumphantly bumping genocides and floods off the front page to blare out "This Motherfucker Is OLD! O-L-D!" is beyond ridiculous.